Nonintubated thoracic surgery (NITS) has a good safety record in experienced hands, but has pitfalls for beginners. The main aim of NITS is to keep the patient under spontaneous respiration, avoiding adverse effects, such as hypoxemia, hypercapnia, panic attacks, and finally conversion to general anesthesia. In this paper, the safety aspects of anesthesia for NITS is discussed based on data from the literature and personnel clinical experiences.
Key points
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Knowing indications and contraindications to nonintubated thoracic anesthesia (NITS) is imperative for patient selection and safety.
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Key aim of NITS is to keep the patient under spontaneous respiration avoiding hypoxemia, hypercapnia, panic attacks, and finally conversion to general anesthesia.
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Attention must be payed to pitfalls in premedication, regional anesthesia techniques, spinal opioids, blockage of the cough reflex, and intraoperative sedation.
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A multimodal approach and opioid-free anesthesia for NITS does not replace an effective local anesthesia or a good working regional anesthesia block.
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Stepwise correction of reversible causes of hypoxemia is necessary before a thoroughly planned conversion.
Introduction
In experienced hands, nonintubated thoracic surgery (NITS) achieves an acceptable safety profile. However, NITS is full of pitfalls for beginners. The technique may be adopted either in patiens who are fully awake or under light sedation. In both cases, patients breathe spontaneously without any definitive airway intubation, although some kind of respiratory assistance (eg, manual ventilation or even laryngeal mask) may be set up on occasion. In essence, the main aim of NITS is to keep the patient under spontaneous respiration and avoid adverse effects, such as hypoxemia, hypercapnia, panic attacks, and finally conversion to general anesthesia.
In this article, the safety aspects of anesthesia for NITS are discussed based on data from the literature and on personal clinical experience.
Safety
Thoracic surgery under general anesthesia shows equivalent surgical results compared with awake thoracic surgery and is correlated with lower mortality and morbidity.
Several studies conclude that NITS is superior to thoracic surgery under general anesthesia by reducing operating room time and the incidence of postoperative respiratory infections and acute respiratory distress syndrome, thus lowering mortality rate and improving perioperative outcomes with less need for nursing, lower costs, and shorter hospital stays.
Acquiring knowledge
Only trained staff should participate during NITS. Education and training programs in thoracic surgery with nonintubated patients is needed before starting NITS, ideally in either high-volume centers or, even better, under proctorship. To acquire experience in awake thoracic surgery, surgeons and anesthesiologists should begin with minor procedures in strictly selected patients and in a cooperative environment with all the necessary background knowledge of NITS.
A good way to start is to perform NITS first in simple cases and then to proceed to more complex cases step by step. It should be kept in mind that strict coordination and vigilance are the keys for successful patient management for NITS.
Contraindications
Knowing the contraindications to NITS is imperative for patient selection. Contraindications can be divided into surgical and anesthetic contraindications ( Box 1 ).
General contraindications
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Refusal of the patient
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Inexperienced and poorly cooperative surgical team
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Critical ASA status
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BMI greater than 30 or 35 kg/m 2
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Anesthetic contraindications
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Difficult airways
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ppoFEV1 less than 30%
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Chest deformity
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Pulmonary infection
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Severe cardiopulmonary dysfunction
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Hemodynamically unstable patient
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Coagulopathy
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Contralateral phrenic nervous paralysis
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Persistent cough or excessive airway secretion
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Gastric reflux
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Surgical contraindications
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Coagulopathy
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Extensive pleural adhesion
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Prior pulmonary resection or previous ipsilateral chest surgery
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Clinical stage N2 lung cancer
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Foreseeable surgical difficulties
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Bleeding of pulmonary artery
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Abbreviations: BMI, body mass index; ppoFEV1, predicted postoperative forced expiratory volume in first second.
From an anesthesiology point of view, the following conditions should be regarded as major contraindications to NITS: (1) contralateral phrenic nerve paralysis, (2) expected difficult airway, (3) persistent cough or excessive airway secretion, (4) high risk of aspiration, (5) severe cardiopulmonary dysfunction, and (6) patients with a body mass index (BMI) of >30 kg/m 2 (or >35 kg/m 2 ). In fact, the higher the BMI, the more the anatomic disadvantage of a higher mediastinum-to-chest ratio. Furthermore, an elevated diaphragm, which is very common in these patients, puts them at a higher risk of impaired intraoperative ventilation and atelectasis. Consequently, as morbidly obese patients carry more risks for intraoperative respiratory depression, nonintubated procedures should not be attempted in these patients. Spine deformities and coagulopathy, although not major contraindications to NITS in themselves, do not allow safe insertion of thoracic epidural catheter, so that alternative analgesia techniques should be considered in these cases.
From a surgical point of view, NITS should be avoided in patients with expected extensive pleural adhesions and previous pulmonary resection. NITS in patients scheduled for major resection should be limited to those with stage I non-small-cell lung cancer. In addition, the following conditions may also dictate some caution (see Box 1 ): American Society of Anaesthesiologists status greater than 2, a tumor size of greater than 6 cm, and other foreseeable surgical difficulties complicating vascular dissection or incomplete fissure. However, Elkhouly and Pompeo have reported that NITS might still be feasible in experienced hands, even with conditions that were regarded as major contraindications in early literature. These include pleural adhesions, previous thoracic surgery, neoadjuvant chemotherapy or radiation, central lesions, and chest wall or vascular involvement ( Box 2 ). Furthermore, in contrast to contraindications quoted in the literature, some authors also noticed that the application of NITS can be extended to high-risk patients with poor performance status, compromised respiratory function, and to those older than 80 years. ,
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Diffuse pleural adhesions
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Previous thoracic surgery
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Neoadjuvant chemotherapy or radiation
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Central lesions
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Chest wall or vascular involvement
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High-risk patients with poor preoperative performance status
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Compromised respiratory function
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Elderly patients greater than 80 years
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Terminally ill but stable patients
Indications
From a surgical point of view, there are subgroups of patients who are more likely to benefit from NITS. NITS is ideally suited for patients with pneumothorax in whom there is a risk of increasing air collection, making ventilation conditions more difficult in case of intubation with one-lung ventilation , , , Also, patients with a high risk for ventilator dependency, such as lung transplant candidates, patients with severe neuromuscular disease, patients who have undergone lung transplantation and pregnant women, are better candidates for NITS than for general anesthesia ( Box 3 ). Unfortunately, these patients also have a higher probability of conversion, so that a contingency plan should be well discussed and prepared. In the literature, good results have been reported in these patients using NITS with various analgesia techniques. ,
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Pleural effusion
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Empyema
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Pathologies with chronic collapse of the operated lung
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Pneumothorax
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Lung transplantation
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Pregnancy
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History of difficult intensive care unit weaning from ventilation
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Fast-track thoracic surgery
In other categories of patients, the advantages of NITS are less clear. However, there is a suggestion that it might reduce postoperative adverse events because of less inflammatory impact on the airways. In fact, compartmental airway inflammation has a pivotal role in the development of perioperative complications after general anesthesia, and it may occur even when protective ventilation strategies are adopted. Patients with complex pleural effusion and empyema are already prone to lung collapse, because they tolerate surgical pneumothorax during spontaneous one-lung breathing very well. For this reason, these patients may also be good candidates for NITS. ,
In addition, patients who have already undergone a long weaning process from a ventilator in their past medical history could also be considered for NITS. This is sometimes requested by the patients themselves, when they are willing to avoid such an unpleasant and traumatic experience. In general, NITS might be applied as a part of an integrated fast-track with the objective of shortening hospitalization as much as possible.
Selection
Patient selection for NITS is crucial to avoid tricky pitfalls. Contraindications and indications, as described in Boxes 1–3 , constitute the first criteria for careful patient selection. Patient refusal is a total contraindication for NITS and any persuasion attempts should be avoided. Both the surgeon and anesthetist should have full agreement on offering NITS. Preoperatively, patients and their relatives must be fully informed on the pros and cons of NITS, including the risk of conversion to general anesthesia. This should be reported in the consent form to avoid any misunderstandings.
Premedication
Ideally, one should always use drugs that can be antagonized, such as benzodiazepines with flumazenil. Some patients do not want any premedication, and this needs to be respected. Alternatively, preoperative sessions of hypnosis could also replace pharmaceutical premedication, thereby avoiding respiratory depression induced by premedication.
Monitoring
The following standard monitoring should be applied in preparation of NITS ( Box 4 ): routine monitoring with electrocardiogram, pulse oximetry, noninvasive blood pressure and noninvasive end tidal CO 2 (ETCO 2 ) connected to either a nasal oxygen cannula or an oxygen mask. At least 2 intravenous lines for the operation have to be inserted. One of them is for fluid replacement and the other one for drug administration, mainly for cardiovascular support if necessary. For more difficult cases, for example, patients with severe comorbidities, invasive radial artery monitoring may be needed to control oxygen saturation and to prevent excess hypercapnia. In addition, in high-risk patients, a central venous line is to be inserted, in preference into a femoral vein, to avoid respiratory distress and complications in the thorax region. In the case of thoracic epidural anesthesia, a urinary catheter should be inserted to avoid retention.
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Routine monitoring (electrocardiogram, pulseoxymetry with oxygen saturation, noninvasive blood pressure, noninvasive ETCO 2 attached to a nasal oxygen cannula or an oxygen mask)
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At least 2 intravenous lines
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A urinary catheter in case of epidural anesthesia or surgery of long duration
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Equipment and drugs for conversion and emergency intubation
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Bispectral Index Monitoring
Although the algorithm of the bispectral index does not accurately predict an unconscious state, it can be helpful as an adjunct.
All equipment and drugs for conversion in the case of emergency should also be prepared in advance.
During surgery, except in cases of severe chronic obstructive pulmonary disease (COPD), in which high-flow oxygen could lead to respiratory depression, high-flow oxygen nasal prongs up to 40 L/min can be administered to stabilize the patient and achieve an oxygen saturation of more than 90%. It is critical to maintain the threshold level of the mean arterial pressure above 65 mm Hg and oxygen saturation greater than 90%. When mean arterial pressure falls below 65 mm Hg and/or systolic arterial pressure below 90 mm Hg, fluids should be administered if needed, otherwise vasoactive drugs are to be given. In cases in which epidural-induced hypotension remains resistant to ephedrine, neosynephrine/phenylephrine should be infused. If more than 1,200 μm/min of neosynephrine is required, it can be replaced by noradrenaline. If oxygen saturation is below 90%, noninvasive ventilation should be applied to recruit the lungs in the spontaneously breathing patient.
Epidural and intrathecal opioid analgesia
To achieve the optimal spread of anesthesia, which is in relation to the planned level of surgical incision, the anatomic puncture level of the epidural block should be discussed with the surgeon in advance. Puncture level is usually between T3 and T7. It is important to note that the volume of anesthesia solution that is administered also depends on the length of the incision (the longer the incision the more volume injected) and also varies with the size and weight of the patient.
For obtaining a quick onset of an anesthetic block, lidocaine and chirocaine are the first choices. For long-lasting analgesic effect, administer ropivicaine (7.5 mg/mL) or bupivacaine (5 mg/mL), or higher concentrations. One has to avoid local anesthetic solutions of low concentration, because the patient might feel intrathoracic manipulations, which could lead to pain or panic attacks. Moreover, local anesthetic of high concentration could lead to a motor block, which could contribute to decreasing the tidal volume. However, in my personal experience, high concentrations of ropivacaine 0.75% did not impair spontaneous respiration, even in patients with severe respiratory disease undergoing NITS.
Providing a continuous epidural perfusion is safer than top-up bolusses through the epidural catheter to keep the patients constantly pain-free throughout the procedure and also provide better hemodynamic stability.
The main side effects of thoracic epidural anesthesia are urinary retention and hypotension ( Box 5 ). In addition, liberal administration of intravenous fluids in the case of epidural-induced hypotension could lead to wet lung. Therefore, vasopressors are preferable to obtain a mean arterial pressure of at least 65 mm Hg. Hemodynamic instability caused by hypotension is a common side effect of thoracic epidural anesthesia, although it is rarely observed with continuous paravertebral block ( Box 6 ). The paravertebral block offers the advantages of a unilateral block without bilateral sympathectomy and lower incidence of hypotension. There is also less urinary retention and fewer neurologic complication. In contrast to epidural anesthesia, the paravertebral block also provides an alternative in cases of sepsis, coagulation disorders, neurologic disorders and difficult vertebral anatomy when an epidural is difficult to perform. In this regard, Baidya and colleagues conclude that thoracic paravertebral block may be as effective as thoracic epidural analgesia for postthoracotomy pain relief and is also associated with fewer complications. The paravertebral block offers the advantages of a unilateral block without bilateral sympathectomy and urinary retention. There are also fewer neurologic complications. In contrast to epidural anesthesia, the paravertebral block also provides an alternative in cases of sepsis, coagulation disorders, neurologic disorders, and difficult vertebral anatomy when an epidural is difficult to perform. However, as reported by Beyaz and colleagues , it must be mentioned that equally to thoracic epidural anesthesia, paravertebral block can also lead to a total spinal block. In each case, the benefits of epidural anesthesia have to be counterbalanced with its risks, such as epidural hematomas, spinal nerve injury, phrenic nerve palsy, and inadvertent high anesthetic level (see Boxes 5 and 6 ). In particular, a risk of neurologic complication owing to epidural has been reported as 0.07%. The safety profile of epidural anesthesia was also evaluated by Kang and colleagues, who concluded that serious complications, such as epidural hematoma (0.02%) and postoperative neurologic deficits (1.12%), were very rare. Generally speaking, compared with thoracic surgery under general anesthesia, NITS under thoracic epidural anesthesia provides more advantages than disadvantages, especially in high-risk patients, such as diffuse interstitial lung fibrosis and limb girdle myopathy.
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Hypotension
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Urinary retention
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Inadvertent administration of fluid in case of epidural-induced hypotension
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Pain or panic attacks because of underdosing of local anesthesia solution
Thoracic epidural anesthesia:
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Hemodynamic instability as a result of hypotension
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Bilateral block with possibility for bilateral sympathectomy
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Contraindicated in the case of sepsis or coagulation disorders
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Difficult to perform in the case of difficult vertebral anatomy
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Risk of epidural hematomas
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Risk of spinal nerve injury
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Risk of phrenic nerve palsy
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Risk of inadvertent high anesthetic level
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Well-known technique with large clinical experience in the literature
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Thoracic paravertebral block:
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Less hypotension than thoracic epidural anesthesia
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One sided surgery without bilateral block
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Unilateral block without bilateral sympathectomy
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Lower incidence of hypotension
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Lower incidence of urinary retention
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Feasible in the case of sepsis or coagulation disorders
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Feasible in the case of neurologic disorders
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Feasible in the case of difficult vertebral anatomy
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